去除findViewById

app/src/main/java/io/legado/app/ui/main/MainActivity.kt

@@ -1,17 +1,17 @@
 package io.legado.app.ui.main
 
 import android.os.Bundle
-import com.google.android.material.floatingactionbutton.FloatingActionButton
-import com.google.android.material.snackbar.Snackbar
-import androidx.core.view.GravityCompat
-import androidx.appcompat.app.ActionBarDrawerToggle
+import android.view.Menu
 import android.view.MenuItem
+import androidx.appcompat.app.ActionBarDrawerToggle
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.view.GravityCompat
 import androidx.drawerlayout.widget.DrawerLayout
 import com.google.android.material.navigation.NavigationView
-import androidx.appcompat.app.AppCompatActivity
-import androidx.appcompat.widget.Toolbar
-import android.view.Menu
+import com.google.android.material.snackbar.Snackbar
 import io.legado.app.R
+import kotlinx.android.synthetic.main.activity_main.*
+import kotlinx.android.synthetic.main.app_bar_main.*
 
 class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelectedListener {
 
@@ -19,25 +19,23 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
-        val toolbar: Toolbar = findViewById(R.id.toolbar)
+
         setSupportActionBar(toolbar)
 
-        val fab: FloatingActionButton = findViewById(R.id.fab)
         fab.setOnClickListener { view ->
             Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                 .setAction("Action", null).show()
         }
-        val drawerLayout: DrawerLayout = findViewById(R.id.drawer_layout)
-        val navView: NavigationView = findViewById(R.id.nav_view)
+
         val toggle = ActionBarDrawerToggle(
-            this, drawerLayout, toolbar,
+            this, drawer_layout, toolbar,
             R.string.navigation_drawer_open,
             R.string.navigation_drawer_close
         )
-        drawerLayout.addDrawerListener(toggle)
+        drawer_layout.addDrawerListener(toggle)
         toggle.syncState()
 
-        navView.setNavigationItemSelectedListener(this)
+        nav_view.setNavigationItemSelectedListener(this)
     }
 
     override fun onBackPressed() {